The following abbreviations and terminology (whenever differently stated) are used in the current invention:
TABLE 13GPP3rd Generation Partnership ProjectASAccess Stratum (use similar to RRC signaling in thisinvention)DCNDedicated Core NetworkNB, eNBNode B, evolved Node B (but can also be any ‘RAN node’implementing 2G, 3G, 4G or future 5G technology)E-UTRANEvolved Universal Terrestrial Radio Access Network (alsoused as EUTRAN)GGSNGateway GPRS Support NodeGPRSGeneral Packet Radio ServiceHPLMNHome Public Land Mobile NetworkHSSHome Subscriber ServerIEInformational Element (used as part of a signalling message)MMEMobility Management EntityMNOMobile Network OperatorNASNon Access StratumNFVNetwork Function VirtualizationNNSFNAS/Network Node Selection FunctionPCRFPolicy and Charging Rules FunctionPGWPacket Data Network GatewayPSMPower Saving ModeRAURouting Area UpdateRNCRadio Network ControllerRRCRadio Resource ControlPLMNPublic Land Mobile NetworkSGSNServing GPRS Support NodeSGWServing GatewayTAUTracking Area UpdateUEUser EquipmentUTRANUMTS Terrestrial Radio Access NetworkVPLMNVisited Public Land Mobile Network
The following terminologies are used within this invention.
The terms ‘serving node’ or ‘MME/SGSN’ or ‘MSC/SGSN/MME’ or C-SGN (CIoT Serving Gateway Node) is generally used through the various embodiments of this invention to describe a functional entity like MSC, or SGSN or MME, or C-SGN or other possible control plane functional entity in the mobile network which terminate the control plane signalling (known as NAS signalling) between the core network and the terminal. The serving node (MME/SGSN) can be also a functional entity from future generation networks which is responsible for mobility and session management.
The term HSS/HLR means the repository where the UE's subscription data is stored and can be either an HSS or an HLR or a combined entity.
The terms ‘terminal’, or ‘device’, or ‘user terminal’ or ‘UE’ (User Equipment) or ‘MT’ (Mobile Terminal) are used in an inter-exchangeable manner where all of the terms express the similarly the equipment used to send/receive data and signalling from network or mobile network or radio access network.
In the recent years due to the penetration of Internet of Things (IoT) and Machine-to-Machine (M2M) technologies the standard bodies like 3rd Generation Partnership Project (3GPP) start working on improvements known as Machine Type Communication (MTC) since Release 10. In order to even more reduce the price of end devices and the price in the operator's network for serving such devices, 3GPP carried out a work called Cellular IoT (CIoT). This work studied and evaluated the architecture enhancement to support ultra-low complexity, power constrained, and low data-rate IoT devices. The documentation of this study is captured in the document 3GPPTR23.720. The conclusions were 1) to specify a mandatory control plane (CP) solution, which is documented in section 2 in the TR and 2) to specify optionally user plane (UP) solution, which is documented in section 18 in the TR. Therefore the CP solution is also referenced as ‘solution 2’ and the UP solution is referenced as ‘solution 18’.
The EPS optimized for CIoT supports traffic pattern that is different as compared to the normal UEs and may support only sub-set and necessary functionalities as compared with the existing EPS. An EPS optimized for CIoT can be enabled by having sub-set of functionalities implemented in single logical entity C-SGN (CIoT Serving Gateway Node). Mobility and Attach procedures are performed as described in other clauses for corresponding entities MME, S-GW and P-GW. An example single node non-roaming CIoT architecture is shown in FIG. 1. The detailed description of the reference points (interfaces) can be found in specification 3GPP TS23.401 and 3GPP TS23.682.
The selection between CP or UP solution happens during Attach procedure or during a TAU procedures. The UE indicates a ‘Preferred Network Behaviour’ including the following:                Whether Control Plane CIoT EPS optimisation is supported;        Whether User Plane CIoT EPS optimisation is supported;        Whether Control Plane CIoT EPS optimisation is preferred or whether User Plane Plane CIoT EPS optimisation is preferred;        Whether S1-U data transfer is supported;        Whether SMS transfer without Combined Attach is requested;        Whether Attach without PDN Connectivity is supported.        
The serving node sends in the Attach or TAU accept message the ‘Supported Network Behaviour’ information.
In the CIoT EPS optimisations the UE can support “Attach without PDN connectivity”, which mean that no PDN connectivity, and thus, no EPS bearers are established during the Attach procedure. The UE can request a PDN connectivity (IP or non-IP) at later point of time using NAS (E)SM signaling.
If the serving node configures the CP CIoT EPS optimization to be used, the data is transferred between UE and the serving node in NAS PDUs including the EPS bearer Identity of the PDN connection they relate to. Both the IP and non-IP data types are supported. This is accomplished by using the NAS transport capabilities of RRC and S1-AP protocols and the data transport of GTP-u tunnels between MME and S-GW and between S-GW and P-GW, or if a Non-IP connection is provided by via the MME with the SCEF, then data transfer occurs as indicated in TS 23.682 [74].
FIG. 2 shows a signaling flow of mobile originated (MO) data transmission for Control Plane CIoT EPS Optimisation (i.e. CP solution). This figure is according to TS23.401. When using CP solution for user data transport, the MME (for uplink, UL) and UE (for downlink, DL) uses the EPS Bearer Identity (EBI) contained within the NAS PDUs to identify the associated EPS bearer.
If the MME wishes to use the CP solution for mobile terminating (MT) services, then an example procedure is shown in FIG. 3 from TS23.401.
In order to depict the different protocols involved in the communication between UE and S/PGW, the protocol stacks over the various interfaces are shown in FIG. 4. Please note that this figure shows the protocol stacks for the CP CIoT Optimisations. One main change introduced by the CIoT EPS optimisations is the support of the GTP-U interface over the S11 interface, i.e. between MME and SGW.
In addition the mandatory agreed CP data transmission, it is also possible optionally to use UP data transmission, where the main feature is to the RRC Suspend procedure to store the UE's AS context in the eNB. This procedure is shown in FIG. 5, which is as per TS23.401 section 5.3.4A. Additionally in TS23.401 section 5.3.5A a Connection Resume procedure is described.
The CIoT EPS optimisations can also apply to LTE (EUTRAN) system. In particular, one intention is to cover wide-band (WB) EUTRN UEs (e.g. cat-M) with low cost properties.
However, if a WB EUTRAN UE capable of NB-IoT uses NB-IoT solutions (CP or UP solution), there could be several restrictions when changing RATs. For example, if the UE has activated non-IP connection, then the UE may not reselect 2G/3G access and continue using the non-IP connection.
The non-IP Data Delivery (NIDD) via SCEF will be capture in 3GPP TS23.682, as currently the 3GPP Tdoc S2-160832 (which needs to be implemented in TS23.682) shows the procedures. NIDD may be used to handle mobile originated (MO) and mobile terminated (MT) communication with UEs, where the packets used for the communication are not based on the internet protocol (IP). The configuration of the SCEF for the delivery of the non-IP data is shown in FIG. 6 description and detailed description can be found in 3GPPTdoc S2-160832.
For example purposes, FIG. 7 shows the procedure using which the SCS/AS sends non-IP data to a given user as identified via External Identifier or MSISDN. This procedure assumes that procedures in establishment of EPS bearer for non-IP data and SCEF configuration procedure (as per FIG. 6) are completed.